CN106990318B - Three-phase three-winding transformer medium voltage side ground fault alerts method of discrimination and its device - Google Patents
Three-phase three-winding transformer medium voltage side ground fault alerts method of discrimination and its device Download PDFInfo
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- CN106990318B CN106990318B CN201710424432.9A CN201710424432A CN106990318B CN 106990318 B CN106990318 B CN 106990318B CN 201710424432 A CN201710424432 A CN 201710424432A CN 106990318 B CN106990318 B CN 106990318B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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Abstract
The present invention provides a kind of three-phase three-winding transformer medium voltage side ground fault alarm method of discrimination and its device, how the 110kV substation medium voltage side 35kV system for solving configuration three-phase three-winding transformer correctly judges the technical problem of occurred ground connection alarm property.Obtain the residual voltage setting valve 3U of 35kV power supply line busbar grounding alarm signal0ZDWith 35kV power supply line bus low-voltage setting valve UdZD；It obtains 35kV bus and connects the setting valve 3I for connecing N times power supply line's zero-sequence currents0Izd、3I0IIzd、…3I0Nzd；The A phase, B phase, C phase of bus-bar potential transformer and the secondary fundamental voltage value U of open delta is calculatedA、UB、UCAnd 3UO；Calculate the zero-sequence current 3I that the connected N of 35kV bus goes back to power supply line0I、3I0II…3I0N；By 3UOWith 3U0ZDIt is compared, by min (UA UB UC) and UdZDIt is compared, by 3I0With 3I0zdIt is compared.Particularly suitable field maintenance person operates with, and has ensured the normal work order of substation well.
Description
Technical field
The present invention relates to a kind of method of discrimination of three-phase three-winding transformer medium voltage side ground fault alarm, are suitable for
The alarm of three-phase three-winding transformer medium voltage side small current neutral grounding system ground fault differentiates in 110kV substation.
Background technique
In the 110kV substation for being configured with three-phase three-winding transformer, three-phase transformer is by high-tension side 110kV three-phase
Alternating voltage distinguishes the 10kV three-phase alternating voltage of the 35kV that transformation is medium voltage side and low-pressure side, 35kV and 10kV after transformation
Power supply system is small current neutral grounding system.In the transformer station high-voltage side bus mistake of the 110kV substation of configuration three-phase three-winding transformer
Cheng Zhong, in, downside singlephase earth fault often occurs, therefore, in the 35kV bus of medium voltage side and the 10kV bus of low-pressure side
It is respectively arranged with respective ground connection alarm device, to indicate whether this side system singlephase earth fault occurs, reminds O&M people
Member excludes the ground fault of this side in 1-2 hours, avoids the expansion that causes the accident because of insulation breakdown.In, the ground connection of low-pressure side accuses
The working principle of alarm device is all based on whether this side power supply buses residual voltage occurs, detects when originally flanking ground alarm device
There is residual voltage and is more than the setting valve of residual voltage in this bus, i.e. sending alarm signal.
In the actual motion of the 110kV substation of configuration three-phase three-winding transformer, it often will appear the power supply of the side 10kV
Route load carrying, and the side 35kV power supply line idle running state.If a certain power supply line in the power supply line of the side 10kV
Singlephase earth fault occurs, since the ground connection phase voltage of the route is zero, rather than line voltage can be increased to by being grounded phase-to-ground voltage,
It is possible that the side 35kV neutral point excursion can be caused, the side 35kV power supply buses is caused residual voltage occur, when the residual voltage is more than
When the setting valve of residual voltage, middle pressure 35kV, which flanks ground alarm device, will issue ground connection alarm signal, the ground connection of this falseness
Alarm seriously affects the normal production order；How correctly to judge the ground connection alarm property that 35kV system occurs, becomes configuration
The 110kV substation field of three-phase three-winding transformer is badly in need of the problem to be solved.
Summary of the invention
The present invention provides a kind of three-phase three-winding transformer medium voltage side ground faults to alert method of discrimination, solves configuration
How the 110kV substation medium voltage side 35kV system of three-phase three-winding transformer correctly judges occurred ground connection alarm property
Technical problem.
The present invention is to solve the above technical problem by the following technical programs:
A kind of three-phase three-winding transformer medium voltage side ground fault alarm method of discrimination, is configured with three-phase three-winding transformer
110kV substation, wherein pressure 35kV system occur ground fault alarm method of discrimination the following steps are included:
The first step, the residual voltage setting valve 3U for obtaining 35kV power supply line busbar grounding alarm signal0ZD；Obtain 35kV
Power supply line bus low-voltage setting valve UdZD；
The N times power supply lines that 35kV bus is coupled are ranked up by second step, by first time power supply line subscript I
It indicates；Second time power supply line is indicated with subscript II；And so on, N goes back to power supply line and is indicated with subscript N；
Third step, the N for obtaining 35kV return the setting valve 3I of power supply line's zero-sequence current0Izd、3I0IIzd、…3I0Nzd；
4th step, to the A phase, B phase, C phase of the three-phase three-winding transformer 35kV side bus voltage mutual inductor of substation and
The secondary voltage of open delta is sampled, and instantaneous voltage is obtained, and according to obtained instantaneous voltage, bus electricity is calculated
Press the A phase, B phase, C phase of mutual inductor and the secondary fundamental voltage value U of open deltaA、UB、UCAnd 3UO；
5th step, the electric current that power supply line's protection installation place is gone back to I, II ... the N connected on 35 kV-side of transformer bus are mutual
Sensor A phase secondary current is sampled, and obtains A phase secondary current instantaneous value, and calculate fundamental current amplitude IIA、IIIA…INA
And phase angle thetaIA、θIIA…θNA；The electric current of power supply line's protection installation place is returned to I, II ... the N connected on 35 kV-side of transformer bus
Mutual inductor B phase secondary current is sampled, and obtains B phase secondary current instantaneous value, and calculate fundamental current amplitude IIB、IIIB…
INBAnd phase angle thetaIB、θIIB…θNB；The electricity of power supply line's protection installation place is returned to I, II ... the N connected on 35 kV-side of transformer bus
Current transformer C phase secondary current is sampled, and obtains C phase secondary current instantaneous value, and calculate fundamental current amplitude IIC、
IIIC…INCAnd phase angle thetaIC、θIIC…θNC；
6th step, according to fundamental current amplitude IIA、IIB、IIC、IIIA、IIIB、IIIC…INA、INB、INCAnd phase angle thetaIA、θIB、
θIC、θIIA、θIIB、θIIC…θNA、θNB、θNC, the N that calculates I, II ... returns the zero-sequence current 3I of power supply line0I、3I0II…3I0N；
7th step, the secondary fundamental voltage value 3U by the resulting bus-bar potential transformer open delta of four-step calculationOWith
The setting valve 3U of the residual voltage of the first step0ZDIt is compared, the bus-bar potential transformer three-phase voltage that four-step calculation is gone out
UA、UB、UCIn minimum value and bus low-voltage setting valve UdZDIt is compared:
Work as 3UO≥3U0ZD, and min (UA UB UC)≤UdZDWhen, show that singlephase earth fault, hair occur for 35 kV-side of transformer
It is grounded alarm signal out；
Work as 3UO≥3U0ZD, and min (UA UB UC)>UdZDWhen, the calculated I of the 6th step is returned to the zero sequence electricity of power supply line
Flow 3I0IThe setting valve 3I of power supply line's zero-sequence current is returned with the I of third step0IzdIt is compared:
Work as 3UO≥3U0ZD, and 3I0I≥3I0IzdWhen, show that the I connected on 35 kV-side of transformer bus returns power supply line's hair
Raw singlephase earth fault issues ground connection alarm signal；
Work as 3UO≥3U0ZD, and 3I0I<3I0IzdWhen, then to the II connected on 35 kV-side of transformer bus return power supply lines into
Row differentiates；
Work as 3I0II≥3I0IIzdWhen, show that the II connected on 35 kV-side of transformer bus goes back to power supply line and single-phase earthing occurs
Failure issues ground connection alarm signal；
3I0II<3I0IIzdWhen, then power supply line is returned to the III connected on 35 kV-side of transformer bus and differentiates；
And so on, if m goes back to power supply line in 3UO≥3U0ZD, and 3I0m≥3I0mzdWhen, it issues m and returns power supply line's ground connection
Alarm signal；Otherwise judge that m+1 goes back to power supply line；Until going back to power supply line to N, all differentiation is finished, and such as whole N returns supply lines
Road is without issuing ground connection alarm signal, then there is no ground faults for this side.
The setting valve 3U of residual voltage on 35kV power supply line bus0ZDWith low-voltage definite value UdZDAnd 35kV supply lines
The setting valve 3I of road zero-sequence current0zd, it is to calculate to obtain according to the following formula:
3U0ZD=(0.1-0.3) Un；
UdZD=(0.1-0.3) Un；
3I0zd=(0.01-0.03) IN；
Wherein, UnFor the secondary voltage rating of the voltage transformer on the bus of 35kV power supply line；INFor 35kV supply lines
The secondary rated current of road current transformer.
First set the sampling number of the every cycle of secondary voltage of 35kV side bus voltage mutual inductor open delta as N, then
The voltage sample value of the secondary voltage sampled point of 35kV side bus voltage mutual inductor open delta is u (k), k=0,1,2 ... N-
1, the sampling interval is Δ t；Fourier transform formula is substituted into, the secondary fundamental wave electricity of bus-bar potential transformer open delta is calculated
Pressure value 3UO, the Fourier transform formula of substitution is as follows:
Wherein:
The angular frequency of the secondary voltage cycle of ω -35kV side bus voltage mutual inductor open delta；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
Voltage fundamental amplitude are as follows:
The sampling number of the every cycle of A phase secondary voltage of 35kV side bus voltage mutual inductor is first set as N, then the side 35kV is female
The voltage sample value of the A phase secondary voltage sampled point of line voltage mutual inductor is uA(k), k=0,1,2 ... N-1, sampling interval be
Δt；Fourier transform formula is substituted into, the A phase secondary base WAVE VOLTAGE AMPLITUDE VALUES U of bus-bar potential transformer is calculatedA, Fu of substitution
Vertical leaf transformation formula is as follows:
Wherein:
The angular frequency of the A phase secondary voltage cycle of ω -35kV side bus voltage mutual inductor；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
Voltage fundamental amplitude are as follows:
It can similarly calculate: UBAnd UC。
The A every cycle of phase secondary current of first setting 35 kV-side of transformer power supply line protection installation place current transformer is adopted
Number of samples is N, then the current sampling data of secondary current sampled point is iA(k), k=0,1,2 ... N-1, sampling interval are Δ t；Generation
Enter Fourier transform formula and A phase fundamental current I is calculatedAAnd θA, Fourier transform formula are as follows:
Wherein:
The angular frequency of ω -35 kV-side of transformer power supply line protection installation place current transformer every cycle of A phase secondary current
Rate；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
The A phase secondary current fundamental voltage amplitude of 35 kV-side of transformer power supply line protection installation place current transformer are as follows:
The A phase secondary current fundamental wave phase angle of 35 kV-side of transformer power supply line protection installation place current transformer are as follows:
It can similarly calculate: IB、θBAnd IC、θC；
Utilize IA、θA、IB、θBAnd IC、θC, zero-sequence current 3I can be calculated by bringing following formula into0:
Wherein: a=ej120°For the vector calculus factor.
A kind of three-phase three-winding transformer medium voltage side ground fault alarm discriminating gear, including processor and memory, are deposited
Reservoir alerts computer instruction corresponding to method of discrimination for storing above-mentioned three-phase three-winding transformer medium voltage side ground fault,
Processor is used to read computer instruction and the execution in memory.
The present invention provides the 35kV medium voltage side ground connection alarm in the 110kV substation of configuration three-phase three-winding transformer
Simply and effectively method of discrimination, particularly suitable field maintenance person operate with one kind, have ensured the normal of substation well
Order of work.
Detailed description of the invention
Fig. 1 is wiring schematic diagram of the present invention in 110kV transformer substation system.
Specific embodiment
Below according to attached drawing, the present invention is described in detail:
A kind of three-phase three-winding transformer medium voltage side ground fault alarm method of discrimination, is configured with three-phase three-winding transformer
110kV substation, wherein pressure 35kV system occur ground fault alarm method of discrimination the following steps are included:
The first step, the residual voltage setting valve 3U for obtaining 35kV power supply line busbar grounding alarm signal0ZD；Obtain 35kV
Power supply line bus low-voltage setting valve UdZD；
The N times power supply lines that 35kV bus is coupled are ranked up by second step, by first time power supply line subscript I
It indicates；Second time power supply line is indicated with subscript II；And so on, N goes back to power supply line and is indicated with subscript N；
Third step, the N for obtaining 35kV return the setting valve 3I of power supply line's zero-sequence current0Izd、3I0IIzd、…3I0Nzd；
4th step, to the A phase, B phase, C phase of the three-phase three-winding transformer 35kV side bus voltage mutual inductor of substation and
The secondary voltage of open delta is sampled, and instantaneous voltage is obtained, and according to obtained instantaneous voltage, bus electricity is calculated
Press the A phase, B phase, C phase of mutual inductor and the secondary fundamental voltage value U of open deltaA、UB、UCAnd 3UO；
5th step, the electric current that power supply line's protection installation place is gone back to I, II ... the N connected on 35 kV-side of transformer bus are mutual
Sensor A phase secondary current is sampled, and obtains A phase secondary current instantaneous value, and calculate fundamental current amplitude IIA、IIIA…INA
And phase angle thetaIA、θIIA…θNA；The electric current of power supply line's protection installation place is returned to I, II ... the N connected on 35 kV-side of transformer bus
Mutual inductor B phase secondary current is sampled, and obtains B phase secondary current instantaneous value, and calculate fundamental current amplitude IIB、IIIB…
INBAnd phase angle thetaIB、θIIB…θNB；The electricity of power supply line's protection installation place is returned to I, II ... the N connected on 35 kV-side of transformer bus
Current transformer C phase secondary current is sampled, and obtains C phase secondary current instantaneous value, and calculate fundamental current amplitude IIC、
IIIC…INCAnd phase angle thetaIC、θIIC…θNC；
6th step, according to fundamental current amplitude IIA、IIB、IIC、IIIA、IIIB、IIIC…INA、INB、INCAnd phase angle thetaIA、θIB、
θIC、θIIA、θIIB、θIIC…θNA、θNB、θNC, the N that calculates I, II ... returns the zero-sequence current 3I of power supply line0I、3I0II…3I0N；
7th step, the secondary fundamental voltage value 3U by the resulting bus-bar potential transformer open delta of four-step calculationOWith
The setting valve 3U of the residual voltage of the first step0ZDIt is compared, the bus-bar potential transformer three-phase voltage that four-step calculation is gone out
UA、UB、UCIn minimum value and bus low-voltage setting valve UdZDIt is compared:
Work as 3UO≥3U0ZD, and min (UA UB UC)≤UdZDWhen, show that singlephase earth fault, hair occur for 35 kV-side of transformer
It is grounded alarm signal out；
Work as 3UO≥3U0ZD, and min (UA UB UC)>UdZDWhen, the calculated I of the 6th step is returned to the zero sequence electricity of power supply line
Flow 3I0IThe setting valve 3I of power supply line's zero-sequence current is returned with the I of third step0IzdIt is compared:
Work as 3UO≥3U0ZD, and 3I0I≥3I0IzdWhen, show that the I connected on 35 kV-side of transformer bus returns power supply line's hair
Raw singlephase earth fault issues ground connection alarm signal；
Work as 3UO≥3U0ZD, and 3I0I<3I0IzdWhen, then to the II connected on 35 kV-side of transformer bus return power supply lines into
Row differentiates；
Work as 3I0II≥3I0IIzdWhen, show that the II connected on 35 kV-side of transformer bus goes back to power supply line and single-phase earthing occurs
Failure issues ground connection alarm signal；
3I0II<3I0IIzdWhen, then power supply line is returned to the III connected on 35 kV-side of transformer bus and differentiates；
And so on, if m goes back to power supply line in 3UO≥3U0ZD, and 3I0m≥3I0mzdWhen, it issues m and returns power supply line's ground connection
Alarm signal；Otherwise judge that m+1 goes back to power supply line；Until going back to power supply line to N, all differentiation is finished, and such as whole N returns supply lines
Road is without issuing ground connection alarm signal, then there is no ground faults for this side.
The setting valve 3U of residual voltage on 35kV power supply line bus0ZDWith low-voltage definite value UdZDAnd 35kV supply lines
The setting valve 3I of road zero-sequence current0zd, it is to calculate to obtain according to the following formula:
3U0ZD=(0.1-0.3) Un；
UdZD=(0.1-0.3) Un；
3I0zd=(0.01-0.03) IN；
Wherein, UnFor the secondary voltage rating of the voltage transformer on the bus of 35kV power supply line；INFor 35kV supply lines
The secondary rated current of road current transformer.
First set the sampling number of the every cycle of secondary voltage of 35kV side bus voltage mutual inductor open delta as N, then
The voltage sample value of the secondary voltage sampled point of 35kV side bus voltage mutual inductor open delta is u (k), k=0,1,2 ... N-
1, the sampling interval is Δ t；Fourier transform formula is substituted into, the secondary fundamental wave electricity of bus-bar potential transformer open delta is calculated
Pressure value 3UO, the Fourier transform formula of substitution is as follows:
Wherein:
The angular frequency of the secondary voltage cycle of ω -35kV side bus voltage mutual inductor open delta；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
Voltage fundamental amplitude are as follows:
The sampling number of the every cycle of A phase secondary voltage of 35kV side bus voltage mutual inductor is first set as N, then the side 35kV is female
The voltage sample value of the A phase secondary voltage sampled point of line voltage mutual inductor is uA(k), k=0,1,2 ... N-1, sampling interval be
Δt；Fourier transform formula is substituted into, the A phase secondary base WAVE VOLTAGE AMPLITUDE VALUES U of bus-bar potential transformer is calculatedA, Fu of substitution
Vertical leaf transformation formula is as follows:
Wherein:
The angular frequency of the A phase secondary voltage cycle of ω -35kV side bus voltage mutual inductor；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
Voltage fundamental amplitude are as follows:
It can similarly calculate: UBAnd UC。
The A every cycle of phase secondary current of first setting 35 kV-side of transformer power supply line protection installation place current transformer is adopted
Number of samples is N, then the current sampling data of secondary current sampled point is iA(k), k=0,1,2 ... N-1, sampling interval are Δ t；Generation
Enter Fourier transform formula and A phase fundamental current I is calculatedAAnd θA, Fourier transform formula are as follows:
Wherein:
The angular frequency of ω -35 kV-side of transformer power supply line protection installation place current transformer every cycle of A phase secondary current
Rate；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
The A phase secondary current fundamental voltage amplitude of 35 kV-side of transformer power supply line protection installation place current transformer are as follows:
The A phase secondary current fundamental wave phase angle of 35 kV-side of transformer power supply line protection installation place current transformer are as follows:
It can similarly calculate: IB、θBAnd IC、θC；
Utilize IA、θA、IB、θBAnd IC、θC, zero-sequence current 3I can be calculated by bringing following formula into0:
Wherein: a=ej120°For the vector calculus factor；
Since Fourier transform formula is one of field engineering application common method, it uses in the present invention
This method.
A kind of three-phase three-winding transformer medium voltage side ground fault alarm discriminating gear, including processor and memory, are deposited
Reservoir is by storing based on corresponding to the three-phase three-winding transformer medium voltage side ground fault alarm method of discrimination of this motion offer
The instruction of calculation machine, processor are used to read computer instruction and the execution in memory.
Claims (2)
1. a kind of three-phase three-winding transformer medium voltage side ground fault alerts method of discrimination, configured with three-phase three-winding transformer
110kV substation, wherein pressure 35kV system occur ground fault alarm method of discrimination the following steps are included:
The first step, the residual voltage setting valve 3U for obtaining 35kV power supply line busbar grounding alarm signal0ZD；Obtain 35kV power supply
Line bus low-voltage setting valve UdZD；
The N times power supply lines that 35kV bus is coupled are ranked up by second step, and first time power supply line is indicated with subscript I；
Second time power supply line is indicated with subscript II；And so on, N goes back to power supply line and is indicated with subscript N；
Third step, the N for obtaining 35kV return the setting valve 3I of power supply line's zero-sequence current0Izd、3I0IIzd、…3I0Nzd；
4th step, A phase, B phase, C phase and opening to the three-phase three-winding transformer 35kV side bus voltage mutual inductor of substation
The secondary voltage of triangle is sampled, and instantaneous voltage is obtained, and according to obtained instantaneous voltage, it is mutual that busbar voltage is calculated
The A phase, B phase, C phase of sensor and the secondary fundamental voltage value U of open deltaA、UB、UCAnd 3UO；
5th step, the current transformer A that power supply line's protection installation place is gone back to I, II ... the N connected on 35 kV-side of transformer bus
Phase secondary current is sampled, and obtains A phase secondary current instantaneous value, and calculate fundamental current amplitude IIATo INAAnd phase angle thetaIA
To θNA；The secondary electricity of current transformer B phase of power supply line's protection installation place is returned to I to the N connected on 35 kV-side of transformer bus
Stream is sampled, and obtains B phase secondary current instantaneous value, and calculate fundamental current amplitude IIBTo INBAnd phase angle thetaIBTo θNB；To change
The current transformer C phase secondary current that I to the N connected on depressor 35kV side bus goes back to power supply line's protection installation place is adopted
Sample obtains C phase secondary current instantaneous value, and calculates fundamental current amplitude IICTo INCAnd phase angle thetaICTo θNC；
6th step, according to fundamental current amplitude IIA、IIB、IIC、IIIA、IIIB、IIIC…INA、INB、INCAnd phase angle thetaIA、θIB、θIC、
θIIA、θIIB、θIIC…θNA、θNB、θNC, calculate the zero-sequence current 3I that I to N goes back to power supply line0I、3I0II…3I0N；
7th step, the secondary fundamental voltage value 3U by the resulting bus-bar potential transformer open delta of four-step calculationOWith the first step
Residual voltage setting valve 3U0ZDIt is compared, the bus-bar potential transformer three-phase voltage U that four-step calculation is gone outA、UB、UC
In minimum value and bus low-voltage setting valve UdZDIt is compared:
Work as 3UO≥3U0ZD, and min (UA UB UC)≤UdZDWhen, show that singlephase earth fault occurs for 35 kV-side of transformer, sending connects
Ground alarm signal；
Work as 3UO≥3U0ZD, and min (UA UB UC)>UdZDWhen, the calculated I of the 6th step is returned to the zero-sequence current 3I of power supply line0I
The setting valve 3I of power supply line's zero-sequence current is returned with the I of third step0IzdIt is compared:
Work as 3UO≥3U0ZD, and 3I0I≥3I0IzdWhen, it is single-phase to show that the I connected on 35 kV-side of transformer bus returns power supply line's generation
Ground fault issues ground connection alarm signal；
Work as 3UO≥3U0ZD, and 3I0I<3I0IzdWhen, then power supply line is returned to the II connected on 35 kV-side of transformer bus and sentences
Not；
Work as 3I0II≥3I0IIzdWhen, show that the II connected on 35 kV-side of transformer bus goes back to power supply line and singlephase earth fault occurs,
Issue ground connection alarm signal；
3I0II<3I0IIzdWhen, then power supply line is returned to the III connected on 35 kV-side of transformer bus and differentiates；
And so on, if m goes back to power supply line in 3UO≥3U0ZD, and 3I0m≥3I0mzdWhen, it issues m and returns power supply line's ground connection alarm letter
Number；Otherwise judge that m+1 goes back to power supply line；Until going back to power supply line to N, all differentiation is finished, and such as whole N goes back to power supply lines and do not have
There is sending ground connection alarm signal, then there is no ground faults for this side.
2. a kind of three-phase three-winding transformer medium voltage side ground fault according to claim 1 alerts method of discrimination, special
Sign is, first sets the sampling number of the every cycle of A phase secondary voltage of 35kV side bus voltage mutual inductor as N, then the side 35kV is female
The voltage sample value of the A phase secondary voltage sampled point of line voltage mutual inductor is uA(k), k=0,1,2 ... N-1, sampling interval be
Δt；Fourier transform formula is substituted into, the A phase secondary base WAVE VOLTAGE AMPLITUDE VALUES U of bus-bar potential transformer is calculatedA, Fu of substitution
Vertical leaf transformation formula is as follows:
Wherein:
The angular frequency of the A phase secondary voltage cycle of ω -35kV side bus voltage mutual inductor；
After finding out the sinusoidal coefficients of fundamental wave, then the plural form of fundametal compoment are as follows:
Voltage fundamental amplitude are as follows:
It can similarly calculate: UBAnd UC。
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